Automobile airbag systems have been developed to protect the occupant of a vehicle in the event of a collision by rapidly inflating a cushion or bag between the vehicle occupant and the interior of the vehicle. The inflated airbag absorbs the vehicle occupant's energy to provide a gradual, controlled de-acceleration and provides a cushion to distribute body loads and keep the occupant from impacting the hard surfaces of the vehicle interior.
Much effort has been expended on the development of inflator housings. The inflator housing is the metal shell in which the gas generant is placed and which is ignited by an ignition system when the airbag needs to be inflated. The housing is fitted with the airbag and together they form a critical part of any automobile airbag system. Engineers of automobile airbag systems understand that the design of the housing can influence the performance of the gas generant and the overall safety of the vehicle occupant.
Driver and passenger restraint systems have become commonplace in the automotive industry. Recently, the automotive industry has been installing side impact airbags in automobiles. Side impact airbags present special problems due to size constraints and configuration. The size limitations and location of the inflators require the use of a relatively cool gas to inflate the airbag, otherwise, damage to the bag will be caused by the hot gases.
Hybrid inflators have been proposed as an alternative to the azide and non-azide gas generants. In a hybrid inflator, a canister of pressurized gas is combined with a chemical gas generant. The chemical gas generant, when ignited, ruptures a seal on the pressurized canister and the gases from the canister and the chemical reaction then mix and are used to inflate the airbag.
Hybrid inflators have their own set of problems The major problem deals with reliability over the expected lifetime of the automobile, which may be ten to fifteen years or longer. No matter how carefully the canisters are sealed, leakage occurs through welds and the rupturable seals. If only a portion of the gas escapes over the lifetime of the vehicle, the hybrid inflator will not function properly when called upon to protect a vehicle occupant. In addition, hybrid inflators may not function consistently over a wide temperature range. Further, due to the increased complexity of the hybrid inflator, the costs of production materials and associated labor are prohibitive.
The industry would welcome an improved gas generant type inflator for side airbags, however, as discussed above, the chemical gas generants present potential problems with damage to the bag itself. Through the creative combination of material selection and design, the present invention provides a solution to the problems associated with chemical gas generants for inflators for side airbags.